There have been developed small vehicles like motorcycles and auto bicycles in which, in place of fossil fuel such as gasoline or the like, a fuel battery is mounted as an energy source therefor. In these small vehicles, electric power generated by a fuel battery mounted thereon is supplied to a motor to drive a drive wheel.
As disclosed in Japanese Patent Application Laid-Open Publication No. 2008-213742, in small vehicles mounted with a fuel battery, the fuel battery is disposed in front of a rear wheel, and a power unit equipped with a motor is attached to a frame so as to swing in a vertical direction with respect to the frame. The power unit is provided with a drainpipe for draining water generated within the fuel battery to the outside. The drainpipe is disposed inside and through the fuel battery, and extends up to and beyond the rear wheel. The drainpipe has a drain port formed at the rear end thereof to drain water while preventing the drained water from splashing onto a rider and/or vehicle body.
In a small vehicle mounted with a fuel battery, air is introduced to the fuel battery. The air introduced into the fuel battery has two functions; i.e., a function as an oxidizing agent for causing hydrogen to react within the fuel battery, and a function as a cooling medium for cooling the fuel battery. The air is introduced into the fuel battery using a fan. In order to increase the system efficiency, some fuel battery systems employ a fan, which introduces the air to the fuel battery with low power consumption, to control the fuel battery.
Conventionally a cylindrical pipe of a small diameter is used for the exhaust duct. However, in the conventional cylindrical pipe, the sectional area of the airflow path is too small causing a large pressure loss in the duct path. Therefore, there is a problem that a fan of small power consumption is not suitable for supplying a satisfactory amount of air to the fuel battery. Also, depending on the battery conditions, the fuel battery purges hydrogen to the air exhaust. The hydrogen has to be appropriately diluted and discharged out of the vehicle. Further, the air within the exhaust duct contains water (vapor) generated by the fuel battery. The water of condensed vapor has to be discharged out of the vehicle to prevent the water from being fed back to the fuel battery.
An object of the invention is to provide a small vehicle mounted with a fuel battery using a fan that provides a small output with a small power consumption, to supply a satisfactory amount of air to the fuel battery; and equipped with an exhaust duct capable of reducing the pressure loss and accordingly airflow resistance within, and discharging hydrogen purged from the fuel battery and water in the exhaust duct outwardly of the vehicle.